Porous materials are materials that have porous structures which enable fluids to pass readily through them. Porous membranes enjoy utility in a wide range of divergent applications, including use in fluid filtration to remove solid particulates, use in ultrafiltration to remove colloidal matter from fluids, use as diffusion barriers or separators in electrochemical cells, and uses in gas separation and pervaporation. Porous membranes also have been used in the filtration of antibiotics, beers, oils, bacteriological broths, and for the analysis of air, microbiological samples, intravenous fluids and vaccines. Porous membranes have also seen widespread use as battery separators (e.g., in lithium ion batteries).
Microporous materials generally have pores with an effective diameter typically at least several times the mean free path of the molecules passing through them, namely from several micrometers down to as low as about 100 Angstroms (0.01 micrometers). Ultrafiltration membranes generally have pore sizes below 50 nm, and can be expensive to make due to the materials and processes typically employed.